#include <stdio.h>
int main()
{
    int a;
    while (scanf("%d",&a)!=EOF)
    {
        if (a>100||a<0)printf("Score is error!\n");
        if (a>=0&&a<=59)printf("E\n");
        if (a>=60&&a<=69)printf("D\n");
        if (a>=70&&a<=79)printf("C\n");
        if (a>=80&&a<=89)printf("B\n");
        if (a>=90&&a<=100)printf("A\n");
    }
    return 0;
}